/// <summary>
/// Get all pages in a paginated collection.
/// </summary>
/// <remarks>
/// If <paramref name="progress"/> is non-<see langword="null"/>, the first call to
/// <see cref="IProgress{T}.Report"/> will specify the <paramref name="page"/>
/// argument. After each task to obtain to the next page of results completes,
/// the <see cref="IProgress{T}.Report"/> method will be called again with the
/// new page of results.
/// <para>
/// This method determines that the end of the collection is reached when either of
/// the following conditions is true.
/// </para>
/// <list type="bullet">
/// <item>The <see cref="ReadOnlyCollectionPage{T}.CanHaveNextPage"/> property returns <see langword="false"/>.</item>
/// <item>An empty page is reached.</item>
/// </list>
/// </remarks>
/// <typeparam name="T">The type of elements in the collection.</typeparam>
/// <param name="page">The first page in the collection.</param>
/// <param name="cancellationToken">The <see cref="CancellationToken"/> that the task will observe.</param>
/// <param name="progress">An optional callback object to receive progress notifications. If this is <see langword="null"/>, no progress notifications are sent.</param>
/// <returns>
/// A <see cref="Task"/> object representing the asynchronous operation. When the operation
/// completes successfully, the <see cref="Task{TResult}.Result"/> property will contain a
/// read-only collection containing the complete set of results from the paginated collection.
/// </returns>
/// <exception cref="ArgumentNullException">If <paramref name="page"/> is <see langword="null"/>.</exception>
public static Task <ReadOnlyCollection <T> > GetAllPagesAsync <T>(this ReadOnlyCollectionPage <T> page, CancellationToken cancellationToken, IProgress <ReadOnlyCollectionPage <T> > progress)
{
if (page == null)
{
throw new ArgumentNullException("page");
}
List <T> result = new List <T>();
ReadOnlyCollectionPage <T> currentPage = page;
Func <bool> condition = () => currentPage != null;
Func <Task> body =
() =>
{
if (progress != null)
{
progress.Report(currentPage);
}
result.AddRange(currentPage);
if (currentPage.CanHaveNextPage && currentPage.Count > 0)
{
return(currentPage.GetNextPageAsync(cancellationToken)
.Select(task => currentPage = task.Result));
}
else
{
currentPage = null;
return(CompletedTask.Default);
}
};
return(TaskBlocks.While(condition, body)
.Select(_ => result.AsReadOnly()));
}
/// <summary>
/// Gets the next page in the paginated collection.
/// </summary>
/// <param name="page">A page in the collection.</param>
/// <param name="cancellationToken">The <see cref="CancellationToken"/> that the task will observe.</param>
/// <returns>
/// <para>A <see cref="Task"/> object representing the asynchronous operation. When the task
/// completes successfully, the <see cref="Task{TResult}.Result"/> property will contain
/// a collection containing the next page of results.</para>
/// </returns>
/// <exception cref="ArgumentNullException">If <paramref name="page"/> is <see langword="null"/>.</exception>
/// <exception cref="InvalidOperationException">If <see cref="ReadOnlyCollectionPage{T}.CanHaveNextPage"/> is
/// <see langword="false"/>.</exception>
/// <exception cref="WebException">If the HTTP request does not return successfully.</exception>
public static Task <ReadOnlyCollectionPage <T> > GetNextPageAsync <T>(this ReadOnlyCollectionPage <T> page, CancellationToken cancellationToken)
{
if (page == null)
{
throw new ArgumentNullException("page");
}
return(TaskBlocks.Using(
() => page.PrepareGetNextPageAsync(cancellationToken),
task => task.Result.SendAsync(cancellationToken).Select(innerTask => innerTask.Result.Item2)));
}
